Every year teacher preparation programs invest considerable time and energy in selecting and supporting cooperating teachers who serve as mentors for their student teachers. Given the weight and importance educators place on the student teaching experience and the powerful role it can play in shaping future teachers, it makes sense for teacher preparation programs to identify those practices of cooperating teachers that contribute to quality student teaching experiences. Further, knowledge of highly valued practices can be used to create professional development designed to enhance the mentoring skills of those teachers who serve as cooperating teachers. In this article, the authors present analysis of data from 389 student teachers' evaluations of cooperating teachers. From this data set, the authors identified those practices that student teachers acknowledged as having a positive influence on their professional development. The focus of this article is to codify specific cooperating teacher behaviors that were identified repeatedly in the data set as contributing value to student teacher development. The authors then provide suggestion for how these practices can be addressed in the professional development of cooperating teachers. (Contains 1 table.)